TOXBASEŽ - Updated 07/2003

Paraquat(E)

Updated 7/2003*

 

Type of product:

Weedkiller.

 

Formulations available:

Granules containing 25-80 g/kg
Solutions containing 100 or 200 g/L (not on sale to the public)

Some formulations contain other herbicides but, with the exception of monolinuron (eg Gramonol 5) they are of little toxicological importance.

 

Toxicity:

The fatal dose by ingestion is probably as little as 20 mg paraquat ion/kg (ie more than one sachet of 2.5% granules or 10 mL of the 200 g/L concentrate in an adult). Death has also been reported after intravenous exposure (Hsu, 2003).

Paraquat - ingestion

Updated 7/99

 

Absorption and elimination:

Ingested paraquat is rapidly absorbed and distributed to tissues. It is excreted through the kidneys.

 

Features:

Eating crops recently sprayed - there is no danger provided the paraquat was correctly diluted before application.

Ingestion of 1.5 - 6 g causes nausea, vomiting, a burning sensation in the mouth, throat and chest, diarrhoea and abdominal pain. After 24-36 hours buccal burns appear (paraquat solutions are strongly alkaline) with dysphagia, dysphonia and difficulty in clearing saliva and bronchial secretions. Oesophageal perforation and mediastinitis have been reported.

Hepatocellular jaundice may occur but is usually mild. Renal failure is often evident within 36 hours. Chemical pneumonitis develops within a few days leading either to development of ARDS (shock lung) or to progressive pulmonary fibrosis. The lung lesion is usually, but not invariably, fatal.

Large amounts (more than 6 g) cause shock, pulmonary oedema, metabolic acidosis, cardiac arrhythmias, coma, convulsions and death within 24-48 hours.

 

Management:

1. Give activated charcoal if the patient presents less than 1 hour after ingestion (see later for dosage).

2. Gastric lavage is of doubtful benefit.

3.Syrup of ipecac is inappropriate as all paraquat preparations contain an emetic.

4. Anti-emetics may be given, but are unlikely to be effective.

5. Confirm paraquat absorption by the qualitative urine test (instructions follow).

6. If the urine test is negative within 4h of ingestion there is no risk or need for further investigation or treatment.

7. If the urine is positive request urgent measurement of the plasma paraquat concentration to assess the severity of poisoning (a list of laboratories which can do this follows).

8. Compare the patient's plasma paraquat concentration related to time from ingestion with those in the following table to determine likely outcome.

9. Discuss treatment of potentially fatal cases with the medical staff at your nearest poisons information centre.

10. Replace lost fluids and electrolytes intravenously.

10. Analgesics may be required.

11. Forced diuresis and peritoneal dialysis are ineffective.

12. Avoid giving oxygen as this enhances the toxicity of paraquat.

 

Please complete an on-line questionnaire to tell us about your patient

Paraquat levels and likely outcome

PARAQUAT CONCENTRATIONS

 

	Plasma paraquat  (mg/L)		Time after ingestion (hours)
	2.0	at	4
If less than	0.8	at	5	If more than
	0.6	at	6
	0.48	at	7
LIKELY	0.33	at	8	ALMOST
TO	0.29	at	10	CERTAIN
SURVIVE	0.23	at	12	TO DIE
	0.17	at	15
	0.12	at	20
	0.10	at	24

National Poisons Information Service

Updated 2/2006

There is now a single number for the UK National Poisons Information Service. Calling this number will direct you to one of the NPIS poisons centres

0870 600 6266

Ireland - National Poisons Information Centre

Dublin 00353 1 809 2566

End I>


Paraquat Urine Test

Updated 11/96

1. Add 0.1 g sodium dithionite to 10 mL of 1 molar sodium hydroxide solution. This should be freshly prepared.

2. Add 1 mL of this solution to 1 mL of urine.

If the solution turns:

* blue within seconds - paraquat is present, the darker the blue the greater the concentration

* pale green - diquat or low concentrations of paraquat

Alternatively a Zeneca (ICI) test kit may be used.

NB These tests only confirm paraquat absorption. They are NOT a suitable method of assessing the severity of poisoning or the risk to life.

Paraquat - inhalation

Features after inhalation:

Sore throat, dysphonia and epistaxis have been reported. Pulmonary and
systemic toxicity is not a hazard because the particles produced by most sprays are too large to be inhaled deeper than the larynx

 

Treatment:

Reassure the patient. Symptoms usually disappear in a few days. Give advice on future use of paraquat sprays, particularly to avoid use in windy weather.

End

 

Please complete an on-line questionnaire to tell us about your patient

Paraquat - skin exposure

Updated 7/99

 

Features after skin exposure:

Prolonged contact causes erythema which may progress to ulceration.

Rarely, sufficient paraquat may be absorbed through the skin to cause fatal systemic toxicity. Hepatocellular and renal tubular necrosis are seldom serious and death is due to progressive pulmonary fibrosis and hypoxia as is seen after ingestion.

 

Management:

1. Remove soiled clothing and wash contaminated skin with copious volumes of water (see skin decontamination)

2. Treat skin ulcers conventionally

3. There is no treatment for paraquat induced pulmonary fibrosis.

4. Examine spray canister and hoses for leaks before using again

Skin decontamination - pesticides

10/96

SAFETY FIRST

* Avoid contaminating yourself. Wear protective clothing.

* Do NOT allow smoking nearby. There may be a risk of fire if a solvent
is involved.

* Carry out decontamination in a well-ventilated area, preferably with its own ventilation system.

* The patient should remove soiled clothing and wash him/herself if possible.

* Put soiled clothing in a sealed container to prevent escape of of volatile substances.

* Wash hair and all contaminated skin with liberal amounts of water (preferably warm) and soap.

* Pay special attention to skin folds, fingernails and ears.

NB The intensity of the odour is not necessarily an indication of the toxicity of the pesticide. It may be due to the solvent or have been added as a deterrent.

* A decision on disposal of the clothing (destruction or washing and re-use) can await detailed information about the pesticide.

Chemicals Splashed or Sprayed into the Eyes

Updated 1/2002

 

Features:

Pain, blepharospasm, lachrymation, conjunctivitis, palpebral oedema and photophobia. Acidic and alkaline solutions may cause corneal burns.

Alkaline solutions in particular may penetrate all layers of the eye and find their way into the chambers causing iritis, anterior and posterior synechia, corneal opacification, cataracts, glaucoma and retinal atrophy. Alkali burns to the eyes should be considered an ophthalmic emergency.

 

Management:

1. Remove contact lenses if necessary and immediately irrigate the affected eye thoroughly with water or 0.9% saline for at least 10-15 minutes. Continue until the conjunctival sac pH is normal (7.5 - 8.0), retest after 20 minutes and reirrigate if necessary.

2. Any particles lodged in the conjunctival recesses should be removed.

3. Repeated instillation of local anaesthetics (e.g. amethocaine) may reduce discomfort and help more thorough decontamination.

4. Corneal damage may be detected by instillation of fluorescein.

5. Mydriatic and cycloplegic agents (e.g. cyclopentolate, tropicamide) may reduce discomfort but should not be used in patients with glaucoma.

6. Patients with corneal damage, those who have been exposed to strong acids or alkalis and those whose symptoms do not resolve rapidly should be referred for ophthalmological assessment.

Paraquat(A)